In order to improve the sinterability and controllability of dielectric properties, we focused on self-flux composition. In the case of Ba(Mg1/3Nb2/3)O3, we selected Ba(1-b)NbbOd as self-flux system and investigated correlations between Q-factor and the b value. Interestingly, high Q-value was obtained only at the b=0.45. Moreover, the dielectric constant and tf change linearly by the quantity of Ba0.55Nb0.45Od under keeping up high-Q value. As a result, it was indicated that the dielectric properties could be controlled by the assumption of stoichiometric composition and liquid phase consisted by self-flux.